1,721,057 research outputs found
Indole alkaloids from aerial parts of Vinca sardoa
No full textFrom the aerial parts of Vinca sardoa, seven indole alkaloids were isolated, conoflorine and six plumerane-type indolines. N(1)-methyl-14,15- didehydro-12-hydroxyaspidofractinine, N(1)-methyl-14,15-didehydro-12- methoxyaspidofractinine, N(1)-formyl-14,15-didehydroaspidofractinine, N(1)- formyl-14,15-didehydro-12-hydroxyaspidofractinine and the known, venalstonine and N(1)-methyl-14,15-didehydroaspidofractinine
A comparative chemotaxonomic study on Vinca sardoa stearn and Vinca difformis pourret
No full textThe phytochemical analysis of iridoidic fraction of the aerial parts of Vinca sardoa and Vinca difformis, gave the identification of loganic acid in V. difformis as unique iridoid glucoside, while loganin is also present in V. sardoa. The two taxa highly differ in alkaloids, so the chemotaxonomic classification in two different species is supported
Coffee Assessment Using 1H NMR Spectroscopy and Multivariate Data Analysis: A Review
No full textThe importance of nuclear magnetic resonance (NMR) spectroscopy for the
food industry, including the coffee industry, has led to several studies using this
analytical tool to assess coffee in different scenarios. In this context, this chapter
presents an overview of 1H NMR-based metabolomics analysis used in coffee quality
control. Several articles using 1H NMR associated with multivariate data analysis have
been published to investigate aspects related to quality, authenticity, sensory quality,
production processes, and origin of coffee. In addition, the present review reports the
main chemical shifts of the constituents present in the extracts of green and roasted
coffee beans. The results presented confirm the potential and versatility of 1H NMR
combined with chemometric tools for coffee analysis, playing an important role in
distinguishing and identifying the origins, quality, and purity of coffee. Exploratory
data analysis, classification, and calibration are the most used chemometric methods in
metabolomics applied in the coffee field. The results show the potential of NMR and
multivariate data analysis for coffee authentication
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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